Crosstalk Attenuation for Seismic Imaging

ABSTRACT

Crosstalk attenuation for seismic imaging can include creation of a seismic image based on seismic data including multiples. The seismic image can include causal crosstalk and anti-causal crosstalk. Causal crosstalk and anti-causal crosstalk can be predicted based on the seismic data. The predicted causal crosstalk and the predicted anti-causal crosstalk can be attenuated from the seismic image.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No.62/116,749, filed Feb. 16, 2015, which is incorporated by reference.

BACKGROUND

In the past few decades, the petroleum industry has invested heavily inthe development of marine seismic survey techniques that yield knowledgeof subterranean formations beneath a body of water in order to find andextract valuable mineral resources, such as oil. High-resolution seismicimages of a subterranean formation are helpful for quantitative seismicinterpretation and improved reservoir monitoring. For a typical marineseismic survey, a marine survey vessel tows one or more seismic sourcesbelow the sea surface of the water and over a subterranean formation tobe surveyed for mineral deposits. Seismic receivers may be located on ornear the seafloor, on one or more streamers towed by the marine surveyvessel, or on one or more streamers towed by another vessel. The marinesurvey vessel typically contains marine seismic survey equipment, suchas navigation control, seismic source control, seismic receiver control,and recording equipment. The seismic source control may cause the one ormore seismic sources, which can be air guns, marine vibrators, etc., toproduce acoustic signals at selected times. Each acoustic signal isessentially a sound wavefield that travels down through the water andinto the subterranean formation. At each interface between differenttypes of rock, a portion of the wavefield may be refracted, and anotherportion may be reflected, which may include some scattering, back towardthe body of water to propagate toward the sea surface. The seismicreceivers thereby measure a wavefield that was initiated by theactuation of the seismic source.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an elevation or xz-plane view of marine seismicsurveying in which acoustic signals are emitted by a seismic source forrecording by seismic receivers for processing and analysis in order tohelp characterize the structures and distributions of features andmaterials underlying the surface of the earth.

FIG. 2 illustrates an elevation or plane view of a state representingmarine seismic imaging including primaries represented as rays.

FIG. 3 illustrates an elevation or plane view of a state representingmarine seismic imaging including primaries and multiples represented asrays.

FIG. 4 illustrates an elevation or plane view of a state representingmarine seismic imaging including primaries and multiples represented asrays and including causal crosstalk.

FIG. 5 illustrates an elevation or plane view of a state representingmarine seismic imaging including primaries and multiples represented asrays and including anti-causal crosstalk.

FIG. 6 illustrates an elevation or plane view of a state representingmarine seismic imaging for prediction of causal crosstalk.

FIG. 7 illustrates an elevation or plane view of a state representingmarine seismic imaging including primaries and multiples represented asrays and including a prediction of anti-causal crosstalk.

FIG. 8 illustrates a seismic image of multiples including an image ofsubsurface reflectors, causal crosstalk, and anti-causal crosstalk.

FIG. 9 illustrates a seismic image of a prediction of causal crosstalk.

FIG. 10 illustrates a seismic image of a prediction of anti-causalcrosstalk.

FIG. 11 illustrates a seismic image of multiples after crosstalkattenuation from the seismic image illustrated in FIG. 8.

FIG. 12 illustrates a seismic image of primaries without crosstalk.

FIG. 13 illustrates a diagram of a system for crosstalk attenuation forseismic imaging.

FIG. 14 illustrates a diagram of a machine for crosstalk attenuation forseismic imaging.

FIG. 15 illustrates a method flow diagram for crosstalk attenuation forseismic imaging.

DETAILED DESCRIPTION

The present disclosure is related to crosstalk attenuation for seismicimaging. A seismic source can emit an acoustic signal. Examples ofseismic sources include air guns and marine vibrators, among others.Pressure and particle motion variation as a function of time andposition caused by an acoustic signal from a seismic source or modeledas being emitted by a modeled seismic source is called the “sourcewavefield.” One or more seismic sources can be modeled as a pointsource. Pressure and particle motion variation as a function of time andposition measured by a seismic receiver or modeled as being received bya modeled seismic receiver is called the “receiver wavefield.”

Goals of seismic processing can include mathematically transformingrecorded reflections into seismic images of the earth's subsurface. Forexample, seismic processing methods can include mathematicallysimulating wavefield propagation using a computer, where boundary datafrom a sea surface can be extrapolated into a model of the subsurface.As used herein, propagation is the movement of a wavefield,extrapolation is a simulation of propagation, and migration is a processby which an image is produced through extrapolation of boundary data inspace and/or time to another location, such as the subsurface, toproduce a seismic image. The boundary data at the sea surface canconsist of two parts: a source wavefield, and a receiver wavefield. Somewave equation seismic imaging methods can include extrapolating sourceand receiver wavefields from the sea surface into an earth model (e.g.,subsurface model) and can produce a seismic image by computing thelocations where a source wavefield and a receiver wavefield are inphase.

Primary wavefields (“primaries”) and multiple wavefields (“multiples”)can each be divided into down-going and up-going primaries and multiplesrespectively. As used herein, a down-going primary is a wavefield thatis a reflection of an up-going primary. An up-going primary is areflection of a wavefield emitted by a seismic source. A down-goingmultiple is a reflection of an up-going multiple. An up-going multipleis a reflection of a down-going primary or multiple. Some seismicimaging methods only make use of primaries. However, multiples can carryvaluable information. According to the present disclosure, it can bebeneficial to incorporate multiples in seismic imaging methods. However,correlation based seismic imaging with multiples can generate crosstalk.Crosstalk can be generated by source and receiver wavefields being inphase at locations that are not the same location as a subsurfacereflector. Attenuation of crosstalk can be achieved by post-processingthe seismic image and/or modifying the seismic image conditions. Asdescribed in more detail with respect to FIG. 4, causal crosstalk is afalse indication of an up-going wavefield being in phase with adown-going wavefield. The false indication can correspond to a locationthat is deeper than a location where two different wavefields areactually in phase. The false indication can correspond to a time that islater than a time when two different wavefields are actually in phase.As described in more detail with respect to FIG. 5, anti-causalcrosstalk is a false indication of an up-going wavefield being in phasewith a down-going wavefield that corresponds to a location that isshallower and/or a time that is earlier than a location and/or timewhere and/or where two different wavefields are actually in phase.

Migration using primaries and multiples can include creating differentseismic images by supplying different wavefields as source wavefieldsand/or receiver wavefields. An example of creating different seismicimages by supplying different source and/or receiver wavefields isprovided in Table 1. Table 1 lists corresponding seismic images frommigration (Image 1 to Image 18). Image 19, Image 20, and Image 21 arecreated from post-processing combined Images 1-18. Image 19 is a seismicimage of multiples after causal crosstalk and anti-causal crosstalkattenuation. Image 20 is a combined seismic image of primaries andmultiples after causal crosstalk and anti-causal crosstalk attenuation.Image 21 is a joint seismic image of primaries and multiples aftercausal crosstalk and anti-causal crosstalk attenuation. Migration canuse seismic data, such as source and receiver wavefields, as inputs tocreate a seismic image of a subsurface reflector. The seismic data maybe acquisition data. Crosstalk can be predicted without first creating aseismic image that includes the crosstalk. If the source and receiverwavefields are the same (e.g., if the source and receiver wavefields areprimaries, or if the source and receiver wavefields are first ordermultiple, etc.), the migration can output crosstalk. This type ofcrosstalk is categorized as zeroth (0^(th)) order crosstalk. Otherorders of crosstalk are described herein.

TABLE 1 Source wavefields, receiver wavefields, and seismic images fromcombination of different source receiver wavefield pairs. ReceiverPrimaries + Primaries Multiples Multiples (Receiver A) (Receiver B)(Receiver C) Source Image Point Source Primaries Causal CrosstalkPrimaries + Causal [for Direct Arrival] (Image 1) (Image 2) Crosstalk(Source A) (Image 3) Primaries Anti-causal Crosstalk Multiples + CausalMultiples + Causal (Source B) (only 0^(th) order) Crosstalk Crosstalk +Anti- (Image 4) (Image 5) causal Crosstalk (only 0^(th) order) (Image 6)Multiples Anti-causal Crosstalk Multiples + Causal Multiples + Causal(Source C) (except for 0^(th) order) Crosstalk + Anti- Crosstalk + Anti-(Image 7) causal Crosstalk causal Crosstalk (Image 8) (Image 9)Primaries + Anti-causal Crosstalk Multiples + Causal Multiples + CausalMultiples (Image 10) Crosstalk + Anti- Crosstalk + Anti- (Source D)causal Crosstalk causal Crosstalk (Image 11) (Image 12) Point Source +Primaries + Anti- Multiples + Causal Primaries + Multiples + Primaries +causal Crosstalk Crosstalk + Anti- Causal Crosstalk + Multiples (Image13) causal Crosstalk Anti-causal Crosstalk (Source E) (Image 14) (Image15) Point Source + Primaries + Anti- Multiples + Causal Primaries +Multiples + Primaries causal Crosstalk Crosstalk Causal Crosstalk +(Source F) (only 0^(th) order) (Image 17) Anti-causal Crosstalk (Image16) (only 0^(th) order) (Image 18)

TABLE 2 Terminology versus symbol of variables and operators SymbolObject (variable and operator) P_(U) Up-going wavefield P_(U) ^(p)Up-going primary P_(U) ^(m) ¹ 1^(st) order up-going multiple P_(U) ^(m)² 2^(nd) order up-going multiple P_(D) Down-going wavefield P_(D) ¹Down-going wavefield from a point source or down-going wavefield fromimpulse wavelet P_(D) ^(p) Down-going primary P_(D) ^(m) ¹ 1^(st) orderdown-going multiple P_(D) ^(m) ² 2^(nd) order down-going multiple I(x)Migrated image G*(x, x_(s)) Green's function from the source location(x_(s)) to the subsurface location (x) G(x, x_(r)) Green's function fromthe receiver location (x_(r)) to the subsurface location (x) G*(x_(r),x) Green's function from the subsurface location (x) to the receiverlocation (x_(r)) R(x) Reflectivity x Subsurface location (vector) x_(s)Source location (vector) x_(r) Receiver location (vector) ω Temporalfrequency

It is to be understood the present disclosure is not limited toparticular devices or methods, which may, of course, vary. It is also tobe understood that the terminology used herein is for the purpose ofdescribing particular embodiments only, and is not intended to belimiting. As used herein, the singular forms “a”, “an”, and “the”include singular and plural referents unless the content clearlydictates otherwise. Furthermore, the word “may” is used throughout thisapplication in a permissive sense (i.e., having the potential to, beingable to), not in a mandatory sense (i.e., must). The term “include,” andderivations thereof, mean “including, but not limited to.” The term“coupled” means directly or indirectly connected.

The figures herein follow a numbering convention in which the firstdigit or digits correspond to the drawing figure number and theremaining digits identify an element or component in the drawing.Similar elements or components between different figures may beidentified by the use of similar digits. For example, 109 may referenceelement “09” in FIG. 1, and a similar element may be referenced as 209in FIG. 2. As will be appreciated, elements shown herein can be added,exchanged, and/or eliminated so as to provide a number of additionalembodiments of the present disclosure. In addition, as will beappreciated, the proportion and the relative scale of the elementsprovided in the figures are intended to illustrate certain embodimentsof the present invention, and should not be taken in a limiting sense.

FIG. 1 illustrates an elevation or xz-plane 130 view of marine seismicsurveying in which acoustic signals are emitted by a seismic source 126for recording by seismic receivers 122 for processing and analysis inorder to help characterize the structures and distributions of featuresand materials underlying the surface of the earth. FIG. 1 shows a domainvolume 102 of the earth's surface comprising a subsurface volume 106 ofsediment and rock below the surface 104 of the earth that, in turn,underlies a fluid volume 108 of water having a sea surface 109 such asin an ocean, an inlet or bay, or a large freshwater lake. The domainvolume 102 shown in FIG. 1 represents an example experimental domain fora class of marine seismic surveys. FIG. 1 illustrates a first sedimentlayer 110, an uplifted rock layer 112, second, underlying rock layer114, and hydrocarbon-saturated layer 116. One or more elements of thesubsurface volume 106, such as the first sediment layer 110 and thefirst uplifted rock layer 112, can be an overburden for thehydrocarbon-saturated layer 116. In some instances, the overburden mayinclude salt.

FIG. 1 shows an example of a marine survey vessel 118 equipped to carryout marine seismic surveys. In particular, the marine survey vessel 118can tow one or more streamers 120 (shown as one streamer for ease ofillustration) generally located below the sea surface 109. The streamers120 can be long cables containing power and data-transmission lines(e.g., electrical, optical fiber, etc.) to which seismic receivers maybe coupled. In one type of marine seismic survey, each seismic receiver,such as the seismic receiver 122 represented by the shaded disk in FIG.1, comprises a pair of seismic sensors including a geophone that detectsparticle displacement within the water by detecting particle motionvariation, such as velocities or accelerations, and/or a hydrophone thatdetects variations in pressure. The streamers 120 and the marine surveyvessel 118 can include sensing electronics and data-processingfacilities that allow seismic receiver readings to be correlated withabsolute positions on the sea surface and absolute three-dimensionalpositions with respect to a three-dimensional coordinate system. In FIG.1, the seismic receivers along the streamers are shown to lie below thesea surface 109, with the seismic receiver positions correlated withoverlying surface positions, such as a surface position 124 correlatedwith the position of seismic receiver 122. The marine survey vessel 118can also tow one or more seismic sources 126 that produce acousticsignals as the marine survey vessel 118 and streamers 120 move acrossthe sea surface 109. Seismic sources 126 and/or streamers 120 may alsobe towed by other vessels, or may be otherwise disposed in fluid volume108. For example, seismic receivers may be located on ocean bottomcables or nodes fixed at or near the surface 104, and seismic sources126 may also be disposed in a nearly-fixed or fixed configuration. Forthe sake of efficiency, illustrations and descriptions herein showseismic receivers located on streamers, but it should be understood thatreferences to seismic receivers located on a “streamer” or “cable”should be read to refer equally to receivers located on a towedstreamer, an ocean bottom seismic receiver cable, and/or an array ofnodes.

FIG. 1 shows an expanding, spherical acoustic signal, illustrated assemicircles of increasing radius centered at the seismic source 126,representing a down-going wavefield 128, following an acoustic signalemitted by the seismic source 126. The down-going wavefield 128 is, ineffect, shown in a vertical plane cross section in FIG. 1. The outwardand downward expanding down-going wavefield 128 may eventually reach thesurface 104, at which point the outward and downward expandingdown-going wavefield 128 may partially scatter, may partially reflectback toward the streamers 120, and may partially refract downward intothe subsurface volume 106, becoming elastic acoustic signals within thesubsurface volume 106.

Acquisition and processing techniques can be used to extract up-goingand down-going wavefields. In a marine setting, dual-sensor (e.g.,hydrophone and/or vertical geophone, etc.) and/or down-going andup-going wavefield separation can be used to extract such wavefields.Approximations of up-going and/or down-going wavefields can bedetermined by other methods of deghosting. Up-going and down-goingwavefields can be represented by equation (1) as follows:

$\begin{matrix} \begin{matrix}{P_{U} = {P_{U}^{p} + P_{U}^{m_{1}} + P_{U}^{m_{2}} + \ldots}} & (1.1) \\{P_{D} = {P_{D}^{1} + P_{D}^{p} + P_{D}^{m_{1}} + P_{U}^{m_{2}} + \ldots}} & (1.2)\end{matrix} \} & (1)\end{matrix}$

where P_(U) represents an up-going wavefield and P_(D) represents adown-going wavefield. P_(U) ^(P) represents the primaries of theup-going wavefield, P_(U) ^(m) ¹ represents first order surfacemultiples of the up-going wavefield, P_(U) ^(m) ² represents secondorder surface multiples of the up-going wavefield, etc. P_(D) ¹represents the down-going wavefield from a point source. P_(D) ^(m) ¹represents first order surface multiples of the down-going wavefield,P_(D) ^(m) ² represents the second order surface multiples of thedown-going wavefield, etc.

The components of P_(U) and P_(D) are listed in Table 2. In a migration,P_(D) can be used as an input for a source wavefield, and P_(U) can beused as an input for a receiver wavefield. When different primary andmultiple components in P_(U) and P_(D) are combined during migration,different seismic images can be created as shown in Table 1.

Migration using down-going wavefield data as a generalized sourcewavefield and up-going wavefield data as a generalized receiverwavefield can be represented by Equation 2 as follows:

I(x)=Σ_(ω)Σ_(x) _(s) Σ_(x) _(r) G*(x,x _(s);ω)P* _(D)(x _(s) ,x _(r);ω)G(x _(s) ,x _(r); ω)P _(U)(x _(s) ,x _(r); ω)  (2)

where G(x, x_(r); ω) represents the Green's function from a receiver atthe surface, x_(r), to an image point x in a subsurface, G* (x, x_(s);ω)represents the Green's function from a source at the surface, x_(s),to an image point x in a subsurface, and P_(U) represents and up-goingwavefield and P_(D) represents a down-going wavefield.

A receiver wavefield can be simulated given a source wavefield and asubsurface reflection property (e.g., velocity, reflectivity, impedance,etc.). A one-way finite difference operator can be used to migrate awavefield in the frequency domain. Embodiments are not, however, limitedto a one-way wave equation operator. For example, a two-way waveequation or any ray based operator can be used.

Numerical modeling can include using a down-going wavefield as thesource wavefield. Simulated up-going wavefield data at receivers can berepresented by Equation 3 as follows:

P_(U)(x _(r); ω)=G*(x,x _(s); ω)P* _(D)(x _(s); ω)R(x)G*(x _(r),x;ω)  (3)

where G* (x, x_(s); ω) represents the Green's function from the sourcelocation (x_(s)) to the sea surface reflection point (x), G*(x_(r), x;ω) is the Green's function from the subsurface reflection point (x) tothe receiver location (x_(r)), P*_(D) (x_(s); ω) is the down-goingwavefield used as a source wavefield at the sea surface location(x_(s)), R(x) is the reflectivity at the subsurface location (x), andP_(U)(x_(r); ω) is the simulated up-going wavefield at the receiverlocation (x_(r)).

FIG. 2 illustrates an elevation or plane view of a state representingmarine seismic imaging including primaries represented as rays. Thestate includes a sea surface 209, a surface 204 underlying the seasurface 209, and a subsurface reflector 234 underlying the surface 204.Although only one subsurface reflector 234 is illustrated for ease ofexplanation and illustration, embodiments can include more than onesubsurface reflector. By way of example, the subsurface reflector 234can be associated with a hydrocarbon saturated layer that is the targetof seismic imaging.

A point source 232 is illustrated emitting a down-going point sourcewavefield 237, which is illustrated as a ray. The down-going pointsource wavefield 237 is illustrated reflecting off of the surface 204 asa first up-going primary 240-1. The point where the down-going pointsource wavefield 237 and the first up-going primary 240-1 are in phaseis referred to as a surface image point 235 because it is an image pointat the surface 204. Wave equation seismic imaging methods can migratedown-going and up-going wavefields to produce a seismic image wherethese wavefields are in phase. The first up-going primary 240-1continues up to the sea surface 209 where it can be recorded by a firstseismic receiver 242-1.

The down-going point source wavefield 237 is illustrated as continuingthrough the surface 204 to a subsurface reflector 234, where it reflectsas a second up-going primary 240-2. The point where the down-going pointsource wavefield 237 and the second up-going primary 240-2 are in phaseis referred to as a subsurface image point 236 because it is an imagepoint at the subsurface reflector 234. The second up-going primary 240-2continues up to the sea surface 209 where it can be recorded by a secondseismic receiver 242-2. Although the point source 232, the first seismicreceiver 242-1, and the second seismic receiver 242-2 are illustrated ator near the sea surface 209 for clarity, as will be appreciated by oneof ordinary skill in the art, they can be below the sea surface 209.

FIG. 3 illustrates an elevation or plane view of a state representingmarine seismic imaging including primaries and multiples represented asrays. The state includes a sea surface 309, a surface 304 underlying thesea surface 309, a subsurface reflector 334 underlying the surface 304,a point source 332, a down-going point source wavefield 337, a firstup-going primary 340-1, a second up-going primary 340-2, a first surfaceimage point 335-1, a first subsurface image point 336-1, a first seismicreceiver 342-1, and a second seismic receiver 342-2.

As illustrated in FIG. 3, the first up-going primary 340-1 reflects offof the sea surface 309 at a location coincident with the first seismicreceiver 342-1 and continues down as a down-going primary 338.

The down-going primary 338 is illustrated reflecting off of the surface304 as a first up-going multiple 346-1. The first up-going multiple346-1 is a first order multiple because it is an up-going reflection ofa primary. The down-going primary 338 and the first up-going multiple346-1 are in phase at a second surface image point 335-2. The down-goingprimary 338 is also illustrated reflecting off of the subsurfacereflector 334 as a second up-going multiple 346-2, which is also a firstorder up-going multiple. The down-going primary 338 and the secondup-going multiple 346-2 are in phase at a second subsurface image point336-2. The second up-going multiple 346-2 is illustrated reaching thesea surface 309 at a location coincident with a location of a fourthseismic receiver 342-4.

The first up-going multiple 346-1 is illustrated reflecting off of thesea surface 309 at a location coincident with a location of a thirdseismic receiver 342-3 as a down-going multiple 344. The down-goingmultiple 344 is a first order down-going multiple because it is adown-going reflection of a first order multiple.

The down-going multiple 344 is illustrated reflecting off of the surface304 as a third up-going multiple 346-3. The third up-going multiple346-3 is a second order multiple because it is an up-going reflection ofa first order multiple. The down-going multiple 344 and the thirdup-going multiple 346-3 are in phase at a third surface image point335-3. The third up-going multiple 346-3 is illustrated reaching the seasurface 309 at a location coincident with a location of a fifth seismicreceiver 342-5. The down-going multiple 344 is also illustratedreflecting off of the subsurface reflector 334 as a fourth up-goingmultiple 346-4, which is also a second order up-going multiple. Thedown-going multiple 344 and the fourth up-going multiple 346-4 are inphase at a third subsurface image point 336-3. The fourth up-goingmultiple is illustrated reaching the sea surface 309 at a locationcoincident with a location of a sixth seismic receiver 342-6.

As opposed to primaries, which may be generally transformed into desiredseismic image data, multiples may be generally undesired seismic databecause they do not transform into desired seismic image data, but maybe generally considered to transform into noise. Thus, some previousapproaches make use only of primaries. However, multiples can carryvaluable information and can be used, according to the presentdisclosure, in seismic imaging methods as described herein. Thus, whilesome previous approaches to seismic imaging may seek to removemultiples, at least one embodiment of the present disclosure retains theinformation provided by the multiples without removing the multiples orbefore removing the multiples from the seismic data. However,correlation based seismic imaging with multiples can generatesignificant crosstalk, such as causal crosstalk and/or anti-causalcrosstalk. Such crosstalk can be generated by down-going and up-goingwavefields being in phase at locations that do not correspond togeological reflectors. At least one embodiment of the present disclosurereduces such crosstalk.

FIG. 4 illustrates an elevation or plane view of a state representingmarine seismic imaging including primaries and multiples represented asrays and including causal crosstalk 448. The state includes a seasurface 409, a surface 404, a subsurface reflector 434, a seismic source432, a down-going point source wavefield 437, a third seismic receiver442-3, a fifth seismic receiver 442-5, a down-going primary 438, adown-going multiple 444, a first up-going multiple 446-1, a thirdup-going multiple 446-3, a second surface image point 435-2, and a thirdsurface image point 435-3.

Causal crosstalk 448 is a false indication of an up-going wavefieldbeing in phase with a down-going wavefield. The false indication cancorrespond to a location that is deeper than a location where twodifferent wavefields are actually in phase. The false indication cancorrespond to a time that is later than a time when two differentwavefields are actually in phase. The causal crosstalk 448 appears toindicate that the down-going primary 438 is in phase with the apparentup-going multiple 447 at the false reflector 450. However, in thisexample, neither the false reflector 450, nor the apparent up-goingmultiple 447 actually exist. The fact that the down-going primary 438happens to have a point where it is in phase with an extension of thethird up-going multiple 446-3 can generate undesired seismic image data(causal crosstalk 448) for a reflector that does not actually exist (thefalse reflector 450). This causal crosstalk 448 can appear as noise in aseismic image. The causal crosstalk 448 can be said to correspond to alocation that is deeper than a location where two different wavefieldsare actually in phase because it can be defined by its down-goingcomponent, which is the down-going primary 438. The causal crosstalk 448can be said to correspond to a time that is later than a time where twodifferent wavefields are actually in phase because it can be defined byits down-going component, which is the down-going primary 438. Thedown-going component (which is also the existing component) of thecausal crosstalk 448 (as opposed to the apparent up-going multiple 447)is in phase with the existing first up-going multiple 446-1 at thesecond surface image point 435-2, which is shallower and earlier thanthe causal crosstalk 448.

Although not specifically illustrated as such, FIG. 4 can include otherexamples of causal crosstalk. For example, the first up-going multiple446-1 can be extended down to be in phase with the down-going pointsource wavefield 437. The prediction of causal crosstalk illustrated anddescribed with respect to FIG. 6 addresses this other example of causalcrosstalk.

In a migration, when the seismic source 432 is modeled as a point sourcethat emits a source wavefield, the down-going source (Source A inTable 1) wavefield, and recorded up-going primaries and multiples(Receiver C in Table 1) are used as a receiver wavefield, a seismicimage of primaries can be created with causal crosstalk. An example of acreated seismic image with causal crosstalk is illustrated in Table 1 asImage 3.

The up-going and down-going wavefields can be decomposed according toEquation 4 as follows:

$\begin{matrix} \begin{matrix}{P_{U} = {P_{U}^{p} + P_{U}^{m_{1}} + P_{U}^{m_{2}} + \ldots}} & (4.1) \\{P_{D} = P_{D}^{1}} & (4.2)\end{matrix} \} & (4)\end{matrix}$

where P_(D) ¹ represents the down-going wavefield from a point source,P_(U) ^(p) represents the up-going primaries, P_(U) ^(m) ¹ representsthe first order up-going multiples, P_(U) ^(m) ² represents the secondorder up-going multiples, etc., and the components of P_(U) and P_(D)are listed in Table 2.

By substituting Equation 4 into Equation 2, the created seismic image(Image 3 in Table 1) can include primaries and causal crosstalk, and canbe represented by Equation 5 as follows:

$\begin{matrix} \begin{matrix}{{I(x)} = {\Sigma_{\omega}\Sigma_{x_{s}}\Sigma_{x_{r}}{G^{*}( {x,{x_{s};\omega}} )}{P_{D}^{1*}( {x_{s},{x_{r};\omega}} )}}} & (5.1) \\{{{G( {x,{x_{r};\omega}} )}{P_{U}^{p}( {x_{s},{x_{r};\omega}} )}} +} & \; \\{\Sigma_{\omega}\Sigma_{x_{s}}\Sigma_{x_{r}}{G^{*}( {x,{x_{s};\omega}} )}{P_{D}^{1*}( {x_{s},{x_{r};\omega}} )}} & (5.2) \\{{{G( {x,{x_{r};\omega}} )}{P_{U}^{m\; 1}( {x_{s},{x_{r};\omega}} )}} +} & \; \\{\Sigma_{\omega}\Sigma_{x_{s}}\Sigma_{x_{r}}{G^{*}( {x,{x_{s};\omega}} )}{P_{D}^{1*}( {x_{s},{x_{r};\omega}} )}} & (5.3) \\{{{G( {x,{x_{r};\omega}} )}{P_{U}^{m\; 2}( {x_{s},{x_{r};\omega}} )}} + \ldots} & \;\end{matrix} \} & (5)\end{matrix}$

where Equation 5.1 describes a seismic image of primaries, Equation 5.2describes first order causal crosstalk, and Equation 5.3 describessecond order causal crosstalk.

A data domain of the up-going multiples (Receiver B in Table 1) can bemodeled using down-going primaries and multiples (Source D in Table 1)as a source wavefield. The seismic image from primaries with causalcrosstalk (Image 3 in Table 1) can be used for a subsurface reflectionproperty. A seismic imaging engine (e.g., seismic imaging engine 1376illustrated in FIG. 13) can use one-way wave equation modeling, howeverembodiments are not so limited. The down-going wavefield can berepresented by Equation 6 as follows:

P _(D) =P _(D) ^(p) +P _(D) ^(m) ¹ +P _(D) ^(m) ² +. . .   (6)

where P_(D) ^(p) represents down-going primaries, P_(D) ^(m) ¹represents the first order down-going multiples, P_(D) ^(m) ² representsthe second order down-going multiples, etc., and the components of P_(U)and P_(D) are listed in Table 2. Down-going wavefields can be extractedfrom acquisition and/or processing. In a marine setting this can beachieved using a combination of dual-sensors, for example, a combinationof hydrophones and/or vertical geophones, and down-going and up-goingwavefield separation. Embodiments are not so limited, however, and othermethods of deghosting can be used.

Substituting Equation 5 and Equation 6, the arrival time of a multiplereflection event can be estimated as represented by Equation 7 asfollows:

$\begin{matrix} \begin{matrix}{{P_{U}( {x_{r};\omega} )} = {{{G^{*}( {x,{x_{s};\omega}} )}{P_{D}^{p*}( {x_{s};\omega} )}{I(x)}{G^{*}( {x_{r},{x;\omega}} )}} +}} & (7.1) \\{{{G^{*}( {x,{x_{s};\omega}} )}{P_{D}^{m\; 1*}( {x_{s};\omega} )}{I(x)}{G^{*}( {x_{r},{x;\omega}} )}} +} & (7.2) \\{{{G^{*}( {x,{x_{s};\omega}} )}{P_{D}^{m\; 2*}( {x_{s};\omega} )}{I(x)}{G^{*}( {x_{r},{x;\omega}} )}} + \ldots +} & (7.3) \\{= {P_{U}^{m_{1}} + P_{U}^{m_{2}} + P_{U}^{m_{3}} + \ldots +}} & (7.4) \\{P_{U}^{m_{2}} + P_{U}^{m_{3}} + \ldots +} & (7.5) \\{P_{U}^{m_{3}} + \ldots} & (7.6) \\{= {P_{U}^{m_{1}} + {2P_{U}^{m_{2}}} + {3P_{U}^{m_{3}}} + \ldots}} & (7.7)\end{matrix} \} & (7)\end{matrix}$

The modeling of up-going wavefield P_(U) can include all orders ofmultiples. However embodiments are not limited to including all ordersof multiples. Although the amplitude of modeled multiples can bedifferent from recorded multiples, the arrival and timing of the modeledevents can be identical to those from seismic acquisition. In at leastone embodiment, the up-going multiples are estimated in the data domaindirectly, for example using surface related multiple elimination, whichremoves surface related multiples without using additional informationabout the subsurface.

The up-going multiples (Receiver B in Table 1) can be removed from therecorded data to generate data representing the primaries. For example,up-going multiples can be adaptively removed from the recorded data(Receiver C in Table 1), which can consist of both primaries andmultiples, to generate the data representing the primaries (Receiver Ain Table 1).

A seismic source modeled as a point source (Source A in Table 1) canemit a down-going wavefield, which can be used as a source wavefield.Up-going primaries (Receiver A in Table 1), originating from surfacerelated multiple elimination, can be used as a receiver wavefield. Aseismic image of only primaries (Image 1 in Table 1) can be createdusing the down-going wavefield from a point source as a source wavefieldand up-going primaries as a receiver wavefield. The migration input ofup-going and down-going wavefields can be decomposed as represented byEquation 8 as follows:

$\begin{matrix} \begin{matrix}{P_{U} = P_{U}^{p}} & (8.1) \\{P_{D} = P_{D}^{1}} & (8.2)\end{matrix} \} & (8)\end{matrix}$

Equations 8.1 and 8.2 can be substituted into Equation 2 to yieldEquation 9 as follows:

I(x)=Σ_(ω)Σ_(x) _(s) Σ_(x) _(r) G*(x,x;ω)P _(D) ¹*(x _(s) ,x_(r);ω)G(x,x _(r);ω)P _(U) ^(p)(x _(s) ,x _(r); ω)  (9)

A seismic image from a primaries-only wavefield can be created usingEquation 9. For example, Image 1 in Table 1 can be created usingEquation 9.

FIG. 5 illustrates an elevation or plane view of a state representingmarine seismic imaging including primaries and multiples represented asrays and including anti-causal crosstalk 552. The state includes a seasurface 509, a surface 504, a subsurface reflector 534, a seismic source532, a second up-going primary 540-2, a fourth seismic receiver 542-4, asixth seismic receiver 542-6, a down-going primary 538, a down-goingmultiple 544, a second up-going multiple 546-2, a fourth up-goingmultiple 546-4, a second subsurface image point 536-2, and a thirdsubsurface image point 536-3.

Anti-causal crosstalk 552 is a false indication of an up-going wavefieldbeing in phase with a down-going wavefield that corresponds to alocation that is shallower and/or a time that is earlier than a locationand/or time where and/or where two different wavefields are actually inphase. The anti-causal crosstalk 552 appears to indicate that thedown-going multiple 544 is in phase with the second up-going multiple546-2 at the false reflector 550. However, the second up-going multiple546-2 is not a reflection of the down-going multiple 544. Instead, thesecond up-going multiple 546-2 is a reflection of the down-going primary538 at the subsurface image point 536-2. The fact that the secondup-going multiple 546-2 happens to have a point where it is in phasewith the down-going multiple 544 can generate undesired seismic imagedata (anti-causal crosstalk 552) for a reflector that does not actuallyexist (the false reflector 550). This anti-causal crosstalk 552 canappear as noise in a seismic image. The anti-causal crosstalk 552 issaid to correspond to a location that is shallower and/or a time that isearlier than a location and/or time where and/or where two differentwavefields are actually in phase because it can be defined by itsdown-going component, which is the down-going multiple 544. Thedown-going component of the anti-causal crosstalk 552 is in phase withthe fourth up-going multiple 546-4 at the third subsurface image point536-3, which is deeper and later than the anti-causal crosstalk 552.

FIG. 6 illustrates an elevation or plane view of a state representingmarine seismic imaging for prediction of causal crosstalk 649. The stateincludes a sea surface 609, a surface 604, a subsurface reflector 634, afalse reflector 650, and a seismic source 632.

In at least one embodiment, for prediction of causal crosstalk, theseismic source 632 is modeled as a point source (Source A in Table 1)that emits the down-going point source wavefield 637. Up-goingmultiples, such as the up-going multiple 646, which can be received at aseismic receiver 642, can be used as a receiver wavefield (Receiver B inTable 1 by estimation of multiples). Locations where a down-going pointsource wavefield 637 is in phase with an up-going multiple 646 canconstitute a prediction of causal crosstalk 649 (Image 2 in Table 1).

A migration input up-going wavefield and down-going wavefield can bedecomposed as:

$\begin{matrix} \begin{matrix}{P_{U} = {P_{U}^{m\; 1} + P_{U}^{m\; 2} + \ldots}} & (10.1) \\{P_{D} = P_{D}^{1}} & (10.2)\end{matrix} \} & (10)\end{matrix}$

Equation (10.1) and (10.2) can be substituted into equation (2) to yieldequation (11) as follows:

$\begin{matrix} \begin{matrix}\begin{matrix}{{I(x)} = {\Sigma_{\omega}\Sigma_{x_{s}}\Sigma_{x_{r}}{G^{*}( {x,{x_{s};\omega}} )}{P_{D}^{1 -}( {x_{s},{x_{r};\omega}} )}}} \\{{G( {x,{x_{r};\omega}} ){P_{U}^{m\; 1}( {x_{s},{x_{r};\omega}} )}} +}\end{matrix} & (11.1) \\\begin{matrix}{\Sigma_{\omega}\Sigma_{x_{s}}\Sigma_{x_{r}}{G^{*}( {x,{x_{s};\omega}} )}{P_{D}^{1*}( {x_{s},{x_{r};\omega}} )}} \\{{G( {x,{x_{r};\omega}} ){P_{U}^{m\; 2}( {x_{s},{x_{r};\omega}} )}} + \ldots}\end{matrix} & (11.2)\end{matrix} \} & (11)\end{matrix}$

where equation (11.1) represents a first order causal crosstalk andequation (11.2) represents a second order causal crosstalk. In at leastone embodiment, all orders of causal crosstalk (Image 2 in Table 1) arebe predicted using only one migration.

In at least one embodiment, the causal crosstalk (Image 2 in Table 1) iscomputed by auto-convolution of the receiver wavefield (Receiver C inTable 1) using, for example, equation (4.1), which consists of bothprimaries and multiples at the sea surface as represented by equation(12) as follows:

$\begin{matrix} \begin{matrix}\begin{matrix}{{I(x)} = {\Sigma_{\omega}\Sigma_{x_{s}}\Sigma_{x_{r}}{G^{*}( {x,{x_{r};\omega}} )}{P_{U}^{p}( {x_{s},{x_{r};\omega}} )}}} \\{{G( {x,{x_{r};\omega}} ){P_{U}^{p}( {x_{s},{x_{r};\omega}} )}} +}\end{matrix} & (12.1) \\\begin{matrix}{\Sigma_{\omega}\Sigma_{x_{s}}\Sigma_{x_{r}}{G^{*}( {x,{x_{r};\omega}} )}{P_{D}^{p}( {x_{s},{x_{r};\omega}} )}} \\{{G( {x,{x_{r};\omega}} ){P_{U}^{m\; 1}( {x_{s},{x_{r};\omega}} )}} +}\end{matrix} & (12.2) \\\begin{matrix}{\Sigma_{\omega}\Sigma_{x_{s}}\Sigma_{x_{r}}{G^{*}( {x,{x_{r};\omega}} )}{P_{D}^{m\; 1}( {x_{s},{x_{r};\omega}} )}} \\{{G( {x,{x_{r};\omega}} ){P_{U}^{p}( {x_{s},{x_{r};\omega}} )}} +}\end{matrix} & (12.3) \\\begin{matrix}{\Sigma_{\omega}\Sigma_{x_{s}}\Sigma_{x_{r}}{G^{*}( {x,{x_{r};\omega}} )}{P_{D}^{m\; 1}( {x_{s},{x_{r};\omega}} )}} \\{{G( {x,{x_{r};\omega}} ){P_{U}^{m\; 1}( {x_{s},{x_{r};\omega}} )}} + \ldots}\end{matrix} & (12.4)\end{matrix} \} & (12)\end{matrix}$

where equation (12.1) represents a first order causal crosstalk,equation (12.2) represents a second order causal crosstalk, etc.

In the depth domain, the causal crosstalk (Image 2 in Table 1) can beadaptively removed from the seismic image of primaries with causalcrosstalk (Image 3 in Table 1) to create a seismic image of onlyprimaries (Image 1). A seismic image of only primaries can be equivalentto a seismic image created using the method described in conjunctionwith Equation 9.

FIG. 7 illustrates an elevation or plane view of a state representingmarine seismic imaging including primaries and multiples represented asrays and including a prediction of anti-causal crosstalk 753. The stateincludes a sea surface 709, a surface 704, a subsurface reflector 734, afalse reflector 750, and a seismic source 732.

At least one embodiment includes seismic imaging of all orders ofrecorded surface related multiples with causal crosstalk and anti-causalcrosstalk, causal crosstalk prediction, anti-causal crosstalkprediction, both causal crosstalk and anti-causal crosstalk attenuation,and combination of a seismic image of primaries and a seismic image ofmultiples. Down-going primaries and multiples (Source D in Table 1) canbe used as a source wavefield and the up-going primaries and multiples(Receiver C in Table 1) can be used as a receiver wavefield to create aseismic image from multiples (Image 12 in Table 1). A seismic image frommultiples can include both causal crosstalk and anti-causal crosstalk.As an example, the up-going and down-going wavefields can be decomposedas represented by equation (13) as follows:

$\begin{matrix} \begin{matrix}{P_{U} = {P_{U}^{p} + P_{U}^{m_{1}} + \ldots}} & (13.1) \\{P_{D} = {P_{D}^{p} + P_{D}^{m_{1}} + \ldots}} & (13.2)\end{matrix} \} & (13)\end{matrix}$

Equation 13 can be substituted in Equation 2 to yield Equation 14 asfollows:

$\begin{matrix} \begin{matrix}\begin{matrix}{{I(x)} = {\Sigma_{\omega}\Sigma_{x_{s}}\Sigma_{x_{r}}{G^{*}( {x,{x_{s};\omega}} )}{P_{D}^{p*}( {x_{s},{x_{r};\omega}} )}}} \\{{{G( {x,{x_{r};\omega}} )}{P_{U}^{m\; 1}( {x_{s},{x_{r};\omega}} )}} +}\end{matrix} & (14.1) \\\begin{matrix}{\Sigma_{\omega}\Sigma_{x_{s}}\Sigma_{x_{r}}{G^{*}( {x,{x_{s};\omega}} )}{P_{D}^{m\; 1}( {x_{s},{x_{r};\omega}} )}} \\{{{G( {x,{x_{r};\omega}} )}{P_{U}^{m\; 2}( {x_{s},{x_{r};\omega}} )}} + \ldots +}\end{matrix} & (14.2) \\\begin{matrix}{\Sigma_{\omega}\Sigma_{x_{s}}\Sigma_{x_{r}}{G^{*}( {x,{x_{s};\omega}} )}{P_{D}^{p*}( {x_{s},{x_{r};\omega}} )}} \\{{{G( {x,{x_{r};\omega}} )}{P_{U}^{m\; 2}( {x_{s},{x_{r};\omega}} )}} + \ldots}\end{matrix} & (14.3) \\\begin{matrix}{\Sigma_{\omega}\Sigma_{x_{s}}\Sigma_{x_{r}}{G^{*}( {x,{x_{s};\omega}} )}{P_{D}^{p*}( {x_{s},{x_{r};\omega}} )}} \\{{{G( {x,{x_{r};\omega}} )}{P_{U}^{p}( {x_{s},{x_{r};\omega}} )}} +}\end{matrix} & (14.4) \\\begin{matrix}{\Sigma_{\omega}\Sigma_{x_{s}}\Sigma_{x_{r}}{G^{*}( {x,{x_{s};\omega}} )}{P_{D}^{m\; 1}( {x_{s},{x_{r};\omega}} )}} \\{{{G( {x,{x_{r};\omega}} )}{P_{U}^{p}( {x_{s},{x_{r};\omega}} )}} +}\end{matrix} & (14.5) \\\begin{matrix}{\Sigma_{\omega}\Sigma_{x_{s}}\Sigma_{x_{r}}{G^{*}( {x,{x_{s};\omega}} )}{P_{D}^{m\; 1}( {x_{s},{x_{r};\omega}} )}} \\{{{G( {x,{x_{r};\omega}} )}{P_{U}^{m\; 1}( {x_{s},{x_{r};\omega}} )}} + \ldots}\end{matrix} & (14.6)\end{matrix} \} & (14)\end{matrix}$

Different sources of crosstalk that can be present in a seismic imagecan be identified using Equation 14. Seismic imaging with multiples canbe simplified since Equation 13 includes only one order of multiples inthe source wavefield and two orders of multiples in the receiverwavefield.

Prediction of causal crosstalk can be performed as described above withrespect to FIG. 6. Prediction of anti-causal crosstalk 753 can includethe use of down-going multiples (Source D in Table 1), such as thedown-going primary 738, as a source wavefield and up-going primaries(Receiver A in Table 1), such as the second up-going primary 740-2,which can be received at the second seismic receiver 742-2, as areceiver wavefield to create a seismic image of anti-causal crosstalk(Image 10 in Table 1), which can be a noise component in the seismicimage from multiples (Image 12 in Table 1). The up-going primaries(receiver A in Table 1) can be extracted using data space surfacerelated multiple elimination or using multiples attenuation, asdescribed above in connection with FIG. 6.

Up-going and down-going wavefield migration inputs can be decomposed asrepresented by Equation 15 as follows:

$\begin{matrix} \begin{matrix}{P_{U} = P_{U}^{p}} & (15.1) \\{P_{D} = {P_{D}^{p} + P_{D}^{m_{1}} + \ldots}} & (15.2)\end{matrix} \} & (15)\end{matrix}$

Equation 15 can be substituted in Equation 2 to yield Equation 16 asfollows:

$\begin{matrix} \begin{matrix}\begin{matrix}{{I(x)} = {\Sigma_{\omega}\Sigma_{x_{s}}\Sigma_{x_{r}}{G^{*}( {x,{x_{s};\omega}} )}{P_{D}^{p*}( {x_{s},{x_{r};\omega}} )}}} \\{{G( {x,{x_{r};\omega}} ){P_{U}^{p}( {x_{s},{x_{r};\omega}} )}} +}\end{matrix} & (16.1) \\\begin{matrix}{\Sigma_{\omega}\Sigma_{x_{s}}\Sigma_{x_{r}}{G^{*}( {x,{x_{s};\omega}} )}{P_{D}^{m\; 1*}( {x_{s},{x_{r};\omega}} )}} \\{{G( {x,{x_{r};\omega}} ){P_{U}^{p}( {x_{s},{x_{r};\omega}} )}} + \ldots}\end{matrix} & (16.2)\end{matrix} \} & (16)\end{matrix}$

Higher order multiples are not shown in Equation 16 for simplicity.However, at least one embodiment provides for prediction of all ordersof anti-causal crosstalk noise (Image 10 in Table 1) using only onemigration.

The causal and/or anti-causal crosstalk in the seismic image frommultiples (Image 12 in Table 1) can be adaptively removed to create acrosstalk attenuated seismic image of multiples (Image 19 in Table 1).Crosstalk attenuated seismic images from primaries (Image 1 in Table 1)and from multiples (Image 19 in Table 1) can be combined to create acrosstalk attenuated seismic image from primaries and multiples (Image20 in Table 1).

FIG. 8 illustrates a seismic image 860 of multiples including an imageof subsurface reflectors, causal crosstalk, and anti-causal crosstalk.The seismic image 860 can also include an image of primaries. That is,the seismic image 860 can be a raw seismic image without processing toremove multiples or crosstalk.

FIG. 9 illustrates a seismic image 962 of a prediction of causalcrosstalk. The prediction of causal crosstalk can be provided asdescribed with respect to FIG. 4 and FIG. 6. The causal crosstalk thatis predicted can be causal crosstalk that is part of the seismic image860 illustrated in FIG. 8.

FIG. 10 illustrates a seismic image 1064 of a prediction of anti-causalcrosstalk. The prediction of anti-causal crosstalk can be provided asdescribed with respect to FIGS. 5 and 7. The anti-causal crosstalk thatis predicted can be anti-causal crosstalk that is part of the seismicimage 860 illustrated in FIG. 8.

FIG. 11 illustrates a seismic image 1166 of multiples after crosstalkattenuation from the seismic image 860 illustrated in FIG. 8. That is,the seismic image 1166 represents the seismic image 860 illustrated inFIG. 8 after the predicted causal crosstalk illustrated in the seismicimage 962 illustrated in FIG. 9 and the anti-causal crosstalkillustrated in the seismic image 1064 in FIG. 10 have been attenuated(e.g., removed) therefrom. The seismic image 1166 can also include animage of primaries.

FIG. 12 illustrates a seismic image 1268 of primaries without crosstalk.The primaries, which are more easily discernable in the seismic image1268 can be the same primaries that can be included in the seismic image860 in FIG. 8 and the seismic image 1166 in FIG. 11.

FIG. 13 illustrates a diagram of a system 1370 for crosstalk attenuationfor seismic imaging. The system 1370 can include a data store 1374, asubsystem 1372, and/or a number of engines (e.g., seismic imaging engine1376, prediction engine 1378 and/or attenuation engine 1380) and can bein communication with the data store 1374 via a communication link. Thesystem 1370 can include additional or fewer engines than illustrated toperform the various functions described herein. The system can representprogram instructions and/or hardware of a machine (e.g., machine 1482 asreferenced in FIG. 14, etc.). As used herein, an “engine” can includeprogram instructions and/or hardware, but at least includes hardware.Hardware is a physical component of a machine that enables it to performa function. Examples of hardware can include a processing resource, amemory resource, a logic gate, etc.

The number of engines can include a combination of hardware and programinstructions that is configured to perform a number of functionsdescribed herein. The program instructions, such as software, firmware,etc., can be stored in a memory resource such as a machine-readablemedium, etc., as well as hard-wired program such as logic. Hard-wiredprogram instructions can be considered as both program instructions andhardware.

The seismic imaging engine 1376 can include a combination of hardwareand program instructions that is configured to create a seismic imagebased on seismic data including multiples. The seismic image can includecausal crosstalk and anti-causal crosstalk. The seismic imaging engine1376 can be configured to create a seismic image that includes causalcrosstalk and anti-causal crosstalk by migration of down-going primariesand multiples as a source wavefield of the seismic data from a seismicsource to a subsurface image point and by migration of up-goingprimaries and multiples as a receiver wavefield of the seismic data froma seismic receiver to the subsurface image point. The seismic imagingengine 1376 can be configured to create the seismic image by applying animaging condition at a subsurface image point. The seismic imagingengine 1376 can be configured to apply one of the group of seismicimaging conditions including deconvolution and cross-correlation at thesubsurface image point. The object of deconvolution is to reverse theeffects of convolution on recorded data, where convolution assumes thatthe recorded data is a combination of a reflectivity function and asource wavefield from a point source. Cross-correlation is a measure ofsimilarity between two wavefields as a function of a time lag applied toone of them.

The prediction engine 1378 can include a combination of hardware andprogram instructions that is configured to predict causal crosstalkbased on the seismic data. The prediction engine 1378 can be configuredto predict anti-causal crosstalk based on the seismic data. Theprediction engine 1378 can be configured to predict the anti-causalcrosstalk by migration of down-going multiples as a source wavefield ofthe seismic data from a seismic source to a subsurface image point andby migration of up-going primaries as a receiver wavefield of theseismic data from a seismic receiver to the subsurface image point. Theprediction engine 1378 can be configured to extract the down-goingmultiples using down-going and up-going wavefield separation of theseismic data and to estimate the up-going primaries using surfacerelated multiple elimination. The prediction engine 1378 can beconfigured to predict the causal crosstalk by migration of a down-goingwavefield as a source wavefield of the seismic data from a seismicsource modeled as a point source to a subsurface image point andmigration of up-going multiples as a receiver wavefield of the seismicdata from a seismic receiver to the subsurface image point. Theprediction engine can include a combination of hardware and programinstructions that is configured to predict the causal crosstalk byauto-convolution of a receiver wavefield of the seismic data thatincludes both primaries and multiples. Auto-convolution of a wavefieldis a convolution of the wavefield with itself. The prediction engine1378 can be configured to extract the source wavefield and the receiverwavefield using down-going and up-going wavefield separation of theseismic data.

The attenuation engine 1380 can include a combination of hardware andprogram instructions that is configured to attenuate the predictedcausal crosstalk and the predicted anti-causal crosstalk from theseismic image. The seismic imaging engine 1376 can be configured tocombine the causal crosstalk and anti-causal crosstalk attenuatedseismic image of the multiples with a crosstalk attenuated seismic imageof primaries to obtain a crosstalk attenuated seismic image of theprimaries and the multiples.

FIG. 14 illustrates a diagram of a machine for crosstalk attenuation forseismic imaging. The machine 1482 can utilize software, hardware,firmware, and/or logic to perform a number of functions. The machine1482 can be a combination of hardware and program instructionsconfigured to perform a number of functions (e.g., actions). Thehardware, for example, can include a number of processing resources 1484and a number of memory resources 1486, such as a machine-readable mediumor other non-transitory memory resources 1486. The memory resources 1486can be internal and/or external to the machine 1482, for example, themachine 1482 can include internal memory resources and have access toexternal memory resources. The program instructions, such asmachine-readable instructions, can include instructions stored on themachine-readable medium to implement a particular function, for example,an action such as crosstalk attenuation for seismic imaging. The set ofmachine-readable instructions can be executable by one or more of theprocessing resources 1484. The memory resources 1486 can be coupled tothe machine 1482 in a wired and/or wireless manner. For example, thememory resources 1486 can be an internal memory, a portable memory, aportable disk, and/or a memory associated with another resource, forexample, enabling machine-readable instructions to be transferred and/orexecuted across a network such as the Internet. As used herein, a“module” can include program instructions and/or hardware, but at leastincludes program instructions.

Memory resources 1486 can be non-transitory and can include volatileand/or non-volatile memory. Volatile memory can include memory thatdepends upon power to store information, such as various types ofdynamic random access memory among others. Non-volatile memory caninclude memory that does not depend upon power to store information.Examples of non-volatile memory can include solid state media such asflash memory, electrically erasable programmable read-only memory, phasechange random access memory, magnetic memory, optical memory, and/or asolid state drive, etc., as well as other types of non-transitorymachine-readable media.

The processing resources 1484 can be coupled to the memory resources1486 via a communication path 1488. The communication path 1488 can belocal or remote to the machine 1482. Examples of a local communicationpath 1488 can include an electronic bus internal to a machine, where thememory resources 1486 are in communication with the processing resources1484 via the electronic bus. Examples of such electronic buses caninclude Industry Standard Architecture, Peripheral ComponentInterconnect, Advanced Technology Attachment, Small Computer SystemInterface, Universal Serial Bus, among other types of electronic busesand variants thereof. The communication path 1488 can be such that thememory resources 1486 are remote from the processing resources 1484,such as in a network connection between the memory resources 1486 andthe processing resources 1484. That is, the communication path 1488 canbe a network connection. Examples of such a network connection caninclude a local area network, wide area network, personal area network,and the Internet, among others.

As shown in FIG. 14, the machine-readable instructions stored in thememory resources 1486 can be segmented into a number of modules 1490,1492, 1494 that when executed by the processing resources 1484 canperform a number of functions. As used herein a module includes a set ofinstructions included to perform a particular task or action. The numberof modules 1490, 1492, 1494 can be sub-modules of other modules. Forexample, the prediction module 1492 can be a sub-module of the seismicimaging module 1490 and/or the prediction module 1492 and the seismicimaging module 1490 can be contained within a single module.Furthermore, the number of modules 1490, 1492, 1494 can compriseindividual modules separate and distinct from one another. Examples arenot limited to the specific modules 1490, 1492, 1494 illustrated in FIG.14.

Each of the number of modules 1490, 1492, 1494 can include programinstructions and/or a combination of hardware and program instructionsthat, when executed by a processing resource 1484, can function as acorresponding engine as described with respect to FIG. 13. For example,the seismic imaging module 1490 can include program instructions and/ora combination of hardware and program instructions that, when executedby a processing resource 1484, can function as the seismic imagingengine 1376, the prediction module 1492 can include program instructionsand/or a combination of hardware and program instructions that, whenexecuted by a processing resource 1484, can function as the predictionengine 1378, and/or the attenuation module 1494 can include programinstructions and/or a combination of hardware and program instructionsthat, when executed by a processing resource 1484, can function as theattenuation engine 1380.

The machine 1482 can include a seismic imaging module 1490, which caninclude instructions to create a first seismic image based on firstseismic data that includes primaries. The seismic imaging module 1490can include instructions to create a second seismic image based onsecond seismic data that includes multiples.

The machine 1482 can include a prediction module 1492, which can includeinstructions to predict first causal crosstalk based on the firstseismic data and predict second causal crosstalk and anti-causalcrosstalk based on the second seismic data. The prediction module 1492can include instructions to predict multiples in the first seismic data.The prediction module 1492 can include instructions to use down-goingprimaries and multiples as a source wavefield of the first seismic dataand use the first seismic data as a subsurface reflection property toestimate the multiples in the first seismic data. The multiples can bean up-going wavefield. The prediction module 1492 can includeinstructions to predict multiples in the first seismic data via surfacerelated multiple elimination.

The machine 1482 can include an attenuation module 1494, which caninclude instructions to attenuate the first causal crosstalk from thefirst seismic image and to attenuate the second causal crosstalk and theanti-causal crosstalk from the second seismic image. The attenuationmodule 1494 can include instructions to attenuate multiples from thefirst seismic data based on the predicted multiples.

The machine 1482 can include a seismic imaging module 1490, which caninclude instructions to combine the causal crosstalk attenuated firstseismic image with the causal crosstalk and anti-causal crosstalkattenuated second seismic image.

In accordance with at least one embodiment of the present disclosure, ageophysical data product may be produced. The geophysical data productmay include, for example, a causal crosstalk and anti-causal crosstalkattenuated seismic image. Geophysical data including seismic data may beobtained and stored on a non-transitory, tangible computer-readablemedium. The geophysical data product may be produced by processing thegeophysical data offshore or onshore either within the United States orin another country. If the geophysical data product is produced offshoreor in another country, it may be imported onshore to a facility in theUnited States. In some instances, once onshore in the United States,geophysical analysis may be performed on the geophysical data product.In some instances, geophysical analysis may be performed on thegeophysical data product offshore. For example, a seismic image can becreated based on the seismic data including multiples, for example as itis being acquired or after it is acquired, offshore to facilitate otherprocessing of the acquired seismic data either offshore or onshore. Theseismic image can include causal crosstalk and anti-causal crosstalk. Asanother example, causal crosstalk and anti-causal crosstalk can bepredicted based on the seismic data, for example as it is being acquiredor after it is acquired, offshore to facilitate other processing of theacquired seismic data either offshore or onshore. As another example,the causal crosstalk and anti-causal crosstalk can be attenuated fromthe seismic image, for example as it is being acquired or after it isacquired, offshore to facilitate other processing of the acquiredseismic data either offshore or onshore.

FIG. 15 illustrates a method flow diagram for crosstalk attenuation forseismic imaging. At block 1596, the method can include creating aseismic image based on seismic data including primaries and multiples.The seismic image can include causal crosstalk and anti-causalcrosstalk. Creating the seismic image can include migrating down-goingprimaries and multiples as a source wavefield from a seismic sourcemodeled as a point source to a subsurface image point and migratingup-going primaries and multiples as a receiver wavefield from a seismicreceiver to the subsurface image point. Creating the seismic image ofthe primaries and the multiples can include applying one of the group ofseismic imaging conditions including deconvolution and cross-correlationat the subsurface image point. The source wavefield and the receiverwavefield can be extracted from down-going and up-going wavefieldseparation of the seismic data.

At block 1597, the method can include predicting causal crosstalk basedon the seismic data. Predicting causal crosstalk can include migrating adown-going wavefield as a source wavefield of the seismic data from aseismic source modeled as a point source to a subsurface image point andmigrating up-going multiples as a receiver wavefield of the seismic datafrom a seismic receiver to the subsurface image point.

At block 1598, the method can include predicting anti-causal crosstalkbased on the seismic data. Predicting anti-causal crosstalk can includemigrating down-going primaries and multiples as a source wavefield ofthe seismic data from a seismic source to a subsurface image point andmigrating up-going primaries as a receiver wavefield of the seismic datafrom a seismic receiver to the subsurface image point.

At block 1599, the method can include attenuating the predicted causalcrosstalk and the predicted anti-causal crosstalk from the seismic data.

The method can include joint seismic imaging of primaries of all ordersof recorded multiples, causal crosstalk prediction, anti-causalcrosstalk prediction, and both causal crosstalk and anti-causalcrosstalk attenuation. Primaries and multiples can be jointly imaged byusing a down-going wavefield, including primaries and multiples (SourceE in Table 1), as a source wavefield from a point source, and anup-going wavefield including primaries and multiples (Receiver C) as areceiver wavefield. A seismic image from joint migration of primariesand multiples (Image 15 in Table 1) can be contaminated by causal and/oranti-causal crosstalk. The migration input up-going and down-goingwavefields can be decomposed as represented by Equation 17 as follows:

$\begin{matrix} \begin{matrix}{P_{U} = {P_{U}^{p} + P_{U}^{m\; 1} + P_{U}^{m\; 2}}} & (17.1) \\{P_{D} = {P_{D}^{1} + P_{D}^{p} + P_{D}^{m\; 1}}} & (17.2)\end{matrix} \} & (17)\end{matrix}$

Equation 17 can be substituted in Equation 2 to yield Equation 18 asfollows:

$\begin{matrix} \begin{matrix}\begin{matrix}{{I(x)} = {\Sigma_{\omega}\Sigma_{x_{s}}\Sigma_{x_{r}}{G^{*}( {x,{x_{s};\omega}} )}{P_{D}^{1*}( {x_{s},{x_{r};\omega}} )}}} \\{{G( {x,{x_{r};\omega}} ){P_{U}^{p}( {x_{s},{x_{r};\omega}} )}} +}\end{matrix} & (18.1) \\\begin{matrix}{\Sigma_{\omega}\Sigma_{x_{s}}\Sigma_{x_{r}}{G^{*}( {x,{x_{s};\omega}} )}{P_{D}^{p*}( {x_{s},{x_{r};\omega}} )}} \\{{G( {x,{x_{r};\omega}} ){P_{U}^{m\; 1}( {x_{s},{x_{r};\omega}} )}} +}\end{matrix} & (18.2) \\\begin{matrix}{\Sigma_{\omega}\Sigma_{x_{s}}\Sigma_{x_{r}}{G^{*}( {x,{x_{s};\omega}} )}{P_{D}^{m\; 1}( {x_{s},{x_{r};\omega}} )}} \\{{G( {x,{x_{r};\omega}} ){P_{U}^{m\; 2}( {x_{s},{x_{r};\omega}} )}} + \ldots +}\end{matrix} & (18.3) \\\begin{matrix}{\Sigma_{\omega}\Sigma_{x_{s}}\Sigma_{x_{r}}{G^{*}( {x,{x_{s};\omega}} )}{P_{D}^{1*}( {x_{s},{x_{r};\omega}} )}} \\{{G( {x,{x_{r};\omega}} ){P_{U}^{m\; 1}( {x_{s},{x_{r};\omega}} )}} +}\end{matrix} & (18.4) \\\begin{matrix}{\Sigma_{\omega}\Sigma_{x_{s}}\Sigma_{x_{r}}{G^{*}( {x,{x_{s};\omega}} )}{P_{D}^{1*}( {x_{s},{x_{r};\omega}} )}} \\{{G( {x,{x_{r};\omega}} ){P_{U}^{m\; 2}( {x_{s},{x_{r};\omega}} )}} +}\end{matrix} & (18.5) \\\begin{matrix}{\Sigma_{\omega}\Sigma_{x_{s}}\Sigma_{x_{r}}{G^{*}( {x,{x_{s};\omega}} )}{P_{D}^{p*}( {x_{s},{x_{r};\omega}} )}} \\{{G( {x,{x_{r};\omega}} ){P_{U}^{m\; 2}( {x_{s},{x_{r};\omega}} )}} + \ldots +}\end{matrix} & (18.6) \\\begin{matrix}{\Sigma_{\omega}\Sigma_{x_{s}}\Sigma_{x_{r}}{G^{*}( {x,{x_{s};\omega}} )}{P_{D}^{p*}( {x_{s},{x_{r};\omega}} )}} \\{{G( {x,{x_{r};\omega}} ){P_{U}^{p}( {x_{s},{x_{r};\omega}} )}} +}\end{matrix} & (18.7) \\\begin{matrix}{\Sigma_{\omega}\Sigma_{x_{s}}\Sigma_{x_{r}}{G^{*}( {x,{x_{s};\omega}} )}{P_{D}^{m\; 1}( {x_{s},{x_{r};\omega}} )}} \\{{G( {x,{x_{r};\omega}} ){P_{U}^{p}( {x_{s},{x_{r};\omega}} )}} +}\end{matrix} & (18.8) \\\begin{matrix}{\Sigma_{\omega}\Sigma_{x_{s}}\Sigma_{x_{r}}{G^{*}( {x,{x_{s};\omega}} )}{P_{D}^{m\; 1}( {x_{s},{x_{r};\omega}} )}} \\{{G( {x,{x_{r};\omega}} ){P_{U}^{p}( {x_{s},{x_{r};\omega}} )}} + \ldots}\end{matrix} & (18.9)\end{matrix} \} & (18)\end{matrix}$

where Equation 18.1 represents a seismic image of primaries, andEquations 18.2 and 18.3 represent seismic images of multiples. Equations18.4-18.6 represent various orders of causal crosstalk, and Equations18.7-18.9 represent various orders of anti-causal crosstalk.

Different sources of crosstalk present in the seismic image (Image 15 inTable 1) can be identified using Equation 18. Joint migration withprimaries and multiples can be simplified since Equation 18 includesonly one order of multiples in the source wavefield and two orders ofmultiples in the receiver wavefield. In Equation 18, the primaries andmultiples can be included in a joint expression. When a direct arrivalis not present, a point source can be scaled to make a seismic image ofthe primaries match a seismic image of the multiples. Differentcrosstalk terms can be predicted in the seismic image space so that thedifferent crosstalk terms can be adaptively attenuated.

At least one embodiment of the present disclosure includes a seismicimaging method. For example, a first method can include seismic imagingof multiples with both causal crosstalk and anti-causal crosstalk,causal crosstalk prediction, anti-causal crosstalk prediction, and bothcausal crosstalk and anti-causal crosstalk attenuation. A second methodcan include joint seismic imaging of primaries and multiples, causalcrosstalk prediction, and both causal crosstalk and anti-causalcrosstalk attenuation. A third method can include seismic imaging ofprimaries with causal crosstalk, causal crosstalk prediction, causalcrosstalk attenuation, and a combination of crosstalk-free seismic imageof primaries with a crosstalk-free seismic image of multiples (e.g. fromthe first method). Embodiments are not constrained to a seismic imagingmethod, however, and one-way wave equation migration and/or two-wayreverse time migration wave equation migration can be used. At least oneembodiment can be applied in a post-stack image domain and/or apre-stack image domain (e.g., subsurface offset and/or angle gathers).

Although specific embodiments have been described above, theseembodiments are not intended to limit the scope of the presentdisclosure, even where only a single embodiment is described withrespect to a particular feature. Examples of features provided in thedisclosure are intended to be illustrative rather than restrictiveunless stated otherwise. The above description is intended to cover suchalternatives, modifications, and equivalents as would be apparent to aperson skilled in the art having the benefit of this disclosure.

The scope of the present disclosure includes any feature or combinationof features disclosed herein (either explicitly or implicitly), or anygeneralization thereof, whether or not it mitigates any or all of theproblems addressed herein. Various advantages of the present disclosurehave been described herein, but embodiments may provide some, all, ornone of such advantages, or may provide other advantages.

In the foregoing Detailed Description, some features are groupedtogether in a single embodiment for the purpose of streamlining thedisclosure. This method of disclosure is not to be interpreted asreflecting an intention that the disclosed embodiments of the presentdisclosure have to use more features than are expressly recited in eachclaim. Rather, as the following claims reflect, inventive subject matterlies in less than all features of a single disclosed embodiment. Thus,the following claims are hereby incorporated into the DetailedDescription, with each claim standing on its own as a separateembodiment.

What is claimed is:
 1. A system, comprising: a seismic imaging engineconfigured to create a seismic image based on seismic data, wherein theseismic data includes multiples, and wherein the seismic image includescausal crosstalk and anti-causal crosstalk; a prediction engineconfigured to: predict causal crosstalk based on the seismic data; andpredict anti-causal crosstalk based on the seismic data; and anattenuation engine configured to attenuate the predicted causalcrosstalk and the predicted anti-causal crosstalk from the seismicimage.
 2. The system of claim 1, wherein the prediction engine isconfigured to predict the anti-causal crosstalk by: migration ofdown-going multiples to a subsurface image point as a source wavefieldof the seismic data; and migration of up-going primaries to thesubsurface image point as a receiver wavefield of the seismic data. 3.The system of claim 2, wherein the prediction engine is configured to:extract the down-going multiples using down-going and up-going wavefieldseparation of the seismic data; and estimate the up-going primariesusing surface related multiple elimination.
 4. The system of claim 2,wherein the seismic imaging engine is configured to create the seismicimage by applying a seismic imaging condition at the subsurface imagepoint.
 5. The system of claim 1, wherein the seismic imaging engine isconfigured to combine the causal crosstalk and anti-causal crosstalkattenuated seismic image of the multiples with a crosstalk attenuatedseismic image of primaries to obtain a crosstalk attenuated seismicimage of the primaries and the multiples.
 6. The system of claim 1,wherein the seismic imaging engine is configured to create the seismicimage by: migration of down-going primaries and multiples to asubsurface image point as a source wavefield of the seismic data; andmigration of up-going primaries and multiples to the subsurface imagepoint as a receiver wavefield of the seismic data.
 7. The system ofclaim 6, wherein the seismic imaging engine is configured to apply oneof the group of seismic imaging conditions including deconvolution andcross-correlation at the subsurface image point.
 8. The system of claim6, wherein the seismic imaging engine is configured to extract thesource wavefield and the receiver wavefield using down-going andup-going wavefield separation of the seismic data.
 9. The system ofclaim 1, wherein the prediction engine is configured to predict thecausal crosstalk by: migration of a down-going wavefield to a subsurfaceimage point as a source wavefield of the seismic data; and migration ofup-going multiples to the subsurface image point as a receiver wavefieldof the seismic data.
 10. The system of claim 1, wherein the predictionengine is configured to predict the causal crosstalk by auto-convolutionof a receiver wavefield of the seismic data that includes both primariesand multiples.
 11. A method, comprising: creating a seismic image basedon seismic data including primaries and multiples, wherein the seismicimage includes causal crosstalk and anti-causal crosstalk; predictingcausal crosstalk based on the seismic data; predicting anti-causalcrosstalk based on the seismic data; and attenuating the predictedcausal crosstalk and the predicted anti-causal crosstalk from theseismic image.
 12. The method of claim 11, wherein predictinganti-causal crosstalk comprises: migrating down-going primaries andmultiples to a subsurface image point as a source wavefield of theseismic data; and migrating up-going primaries to the subsurface imagepoint as a receiver wavefield of the seismic data.
 13. The method ofclaim 11, wherein creating the seismic image comprises: migratingdown-going primaries and multiples to a subsurface image point as asource wavefield of the seismic data; and migrating up-going primariesand multiples to the subsurface image point as a receiver wavefield ofthe seismic data.
 14. The method of claim 13, wherein creating theseismic image of the primaries and the multiples comprises applying oneof the group of seismic imaging conditions including deconvolution andcross-correlation at the subsurface image point.
 15. The method of claim13 including extracting the source wavefield and the receiver wavefieldfrom down-going and up-going wavefield separation of the seismic data.16. The method of claim 11, wherein predicting causal crosstalk in theseismic image comprises: migrating a down-going wavefield as a sourcewavefield of the seismic data from a seismic source modeled as a pointsource to a subsurface image point; and migrating up-going multiples asa receiver wavefield of the seismic data from a seismic receiver to thesubsurface image point.
 17. A non-transitory machine-readable mediumstoring instructions executable by a processing resource to: create afirst seismic image based on first seismic data that includes primaries;create a second seismic image based on second seismic data that includesmultiples; predict first causal crosstalk based on first seismic data;predict second causal crosstalk and anti-causal crosstalk based onsecond seismic data; attenuate the first causal crosstalk from the firstseismic image; attenuate the second causal crosstalk and the anti-causalcrosstalk from the second seismic image; and combine the causalcrosstalk attenuated first seismic image with the causal crosstalk andanti-causal crosstalk attenuated second seismic image.
 18. The medium ofclaim 17, including instructions to: predict multiples in the firstseismic data; and attenuate multiples from the first seismic data basedon the predicted multiples.
 19. The medium of claim 18, includinginstructions to use down-going primaries and multiples as a sourcewavefield of the first seismic data and use the first seismic data as asubsurface reflection property to estimate the multiples in the firstseismic data, wherein the multiples comprise up-going multiples.
 20. Themedium of claim 18, including instructions to estimate the multiples inthe first seismic data via surface related multiple elimination.
 21. Amethod of generating a geophysical data product, the method comprising:obtaining geophysical data including seismic data; processing thegeophysical data to generate the geophysical data product, whereinprocessing the geophysical data comprises: creating a seismic imagebased on the seismic data including multiples, wherein the seismic imageincludes causal crosstalk and anti-causal crosstalk; predicting causalcrosstalk based on the seismic data; predicting anti-causal crosstalkbased on the seismic data; attenuating the predicted causal crosstalkand the predicted anti-causal crosstalk from the seismic image.
 22. Themethod of claim 21, further comprising recording the geophysical dataproduct on a non-transitory machine-readable medium suitable forimporting onshore.
 23. The method of claim 21, wherein processing thegeophysical data comprises processing the geophysical data offshore oronshore.